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Plywoodtype for cab building?

Discussion in 'Amps and Cabs [BG]' started by jock, Aug 22, 2003.


  1. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    Is there a big difference in sound and durability when useing different kinds of plywood? 18mm Pine plywood is much cheaper than 18mm Birch ply. And I see that Aguilar uses Mahogany. What´s up with that?
    Would I be fine with Pineply???
     
  2. You are looking for "void free" when shopping for plywood. Baltic Birch and Appleply are the two I know about. My son-in-law is in the cabinet making business, and is going to get me some BB for my next experiment.

    19mm MDF is 49 pounds per cubic foot
    19mm BB ply is 32 pounds per cubic foot

    I use MDF because it machines cleaner, costs less, and can be purchased at any home emporium. It is sonically superior to the plywoods because it is more dense and weighs a whole lot more. Each of my subwoofer cabs consumes an entire 4x8 sheet of 3/4" MDF. This is 98 pounds just for the material. Add in lots of screws, the driver, covering, electronics, metal grille, and the weight goes up very fast.

    The Eden cabs are successfully built from 5/8" ply and heavily braced. They do not appear to have a buzzing problem.
     
  3. mikemulcahy

    mikemulcahy

    Jun 13, 2000
    The Abyss
    You are correct as always Bruce. My 2 Edens weigh 98 lbs or close to it with casters. No buzz that I am aware of.

    Jock you may also consider the portability of these heavier woods as well. Hernias are expensive and painful.


    Mike
     
  4. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    Thanks, guys.
    BTW how does solid wood compare?
    I can get 18mm boards of solid pine used for shelves real cheap.
     
  5. I wish, but ain't never gonna happen.

    :D

    Solid wood is a poor solution compared to manufactured material. It is much more random in nature and tends to resonate. MDF is the next best thing to poured concrete, and void-free ply is the next best thing to MDF. Each has its advantages (including poured concrete).

    Bracing is the secret. It is labor intensive, which is why you won't find much in manufactured cabs. The XLT series Eden are naturally braced, as both the top and bottom panels of the inner enclosure are braced by the port channels. Excellent design thinking, for sure. Considering the XLT has (4) drivers installed, the top and bottom ports, and metal grille, 98 pounds is quite remarkable.

    Larger panels should be subdivided into smaller panels that are much less prone to resonate. This is done by glue/screw attaching a 1x2 near the middle of the panel. Put another one on the oposite panel and glue/screw a 1x2 stringer between the two. If you are really anal, locate the panel brace off center so it splits the panel into two different size panels.

    Bracing opposing panels to each other will help cancel the pressure induced flexing by counteracting the direction of movement. The baffle panel is usually the weakest point, since it has the large cutout for the driver, port, horn etc. Using 1" or thicker material for the baffle panel is not a bad idea.
     
  6. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    Thanks for making this clear.
    Maybe I´ll try plywood for the cab and MDF for the baffel like Genz Benz have in their cabs.
     
  7. Nightbass

    Nightbass

    May 1, 2001
    Seattle, WA
    No, don't use MDF. Use 5/8" ply for the box and 3/4" ply for the baffle (or the nearest metric equivalents in Sweden). That's really what the mfrs who use 5/8" in their boxes are doing. For the 1x12 I think you are planning, that is the only way to go.
     
  8. jock

    jock

    Jun 7, 2000
    Stockholm, Sweden
    Thanks, your probably right.
    But why not MDF?:meh:
     
  9. The baffle board on a typical 4x10 is mostly open space, so the weight difference between MDF and plywood is not signficant. The weight of the driver(s) should be kept in mind, and the material strength chosen accordingly.

    25mm (1") material is not unreasonable for a baffle board with a lot of driver cut-outs. Glue/screw additional bracing on the rear side to increase rigidity, then brace the baffle to the rear panel.
     
  10. alexclaber

    alexclaber Commercial User

    Jun 19, 2001
    Brighton, UK
    Director - Barefaced Ltd
    Acme have a rather cunning approach that allows them to use thinner ply - each cab is cross-braced and then wooden wedges are hammered in between the brace and the panel thus pre-stressing the panels. It seems to work well - the cabs are pretty light and remarkably uncoloured.

    Those PJB cabs are very heavily braced - unfortunately IMO they're roadie-ready cabs, just too much for a lot of (maybe lazy) gigging bassists.

    Alex
     
  11. thumbtrap

    thumbtrap

    Jun 26, 2003
    Guitar cabinets sometimes are built with solid pine. Then again guitar drivers are usually Qts 1.5-2 with an Fs around the A string, and operate well into frequencies where they're beaming.

    Most of my driver surfing has been aimed at a compact sub. But sometimes I see a particularly bad driver and think - hmmm I wonder if I can find a driver that has an Fs around 100 hz, a peak at 2khz, rolls off like a brick wall at 5khz, and only has at most 90 db 1w/1m, and can handle an honest 100w without thermal destruction. Might make a good "50w combo" speaker to cut down on stage volume.